Dual parison stacked clamp blow molding method

Abstract

A blow molding method including a clamp for clamping two molds in back-to-back relationship, the clamp having first and second movable, inner platens supporting interior sections of two molds; first and second movable outer platens supporting exterior mold sections facing the interior sections; a positioner to move the inner and outer platens between opened and closed positions; an extrusion means to extrude parisons between mold sections, injectors to inject air into the interior of the parisons; and a platen retainer to resiliently position the inner platens between the outer platens to equalize pressure in the two molds.

What is claimed is: 
     
       1. A method for blow molding first and second hollow bodies in two molds, each mold having a movable inner mold section and an outer mold section, with said inner mold sections being in back-to-back alignment in a blow molding apparatus comprising: (a) providing first and second, outwardly facing movable inner mold sections supported on an adjustable central platen;   (b) providing first and second inwardly facing outer mold sections, said first outer mold section facing the first inner mold section, and said second outer mold section facing the second inner mold section;   (c) continuously extruding first and second parisons along parallel pathways;   (d) simultaneously moving said first and second movable inner mold sections outwardly to a first extended and locked position, while moving said outer mold sections outwardly inwardly to a second extended and locked position, said inner mold sections being moved to said first extended and locked position before said outer mold sections are moved to said second extended and locked position, with said first parison being between said first inner mold section and said first outer mold section and said second parison being between said second inner mold section and said second outer mold section;   (e) positioning said central platen relative to said outer mold sections to equalize clamping pressure in said molds when said mold sections are moved to said closed position; and   (f) simultaneously injecting gas into the interiors of said first parison between said first inner and outer mold sections, and into said second parison between said second inner and outer mold sections while said mold sections are in said closed position thereby blow molding said parisons.   
     
     
       2. The method of claim 1, including resiliently positioning said central platen, whereby said central platen adjusts in response to unequal pressure when said mold sections are moved to said closed positions. 
     
     
       3. A method for blow molding first and second hollow bodies in two molds, each mold having a movable inner mold section and an outer mold section, with said inner mold sections being in back-to-back alignment in a blow molding apparatus comprising: (a) providing a plurality of mold clamps, each clamp having first and second, outwardly facing movable inner mold sections supported on an adjustable central platen, and first and second inwardly facing outer mold sections, said first outer mold section facing the first inner mold section, and said second outer mold section facing the second inner mold section;   (b) continually extruding a first parison between said first inner mold section and said first outer mold section, and a second parison between said second inner mold section and said second outer mold section, on each of said clamps as said clamps sequentially pass said parisons;   (c) sequentially moving said clamps past said parisons to position said first parison between said first inner and outer mold sections, and said second parison between said second inner and outer mold sections as each of said clamps sequentially passes said parisons;   (d) simultaneously moving said first and second movable inner mold sections outwardly to a first extended and locked position, while moving said outer mold sections inwardly to a second extended and locked position, said inner mold sections being moved to said first extended and locked position before said outer mold sections are moved to said second extended and locked position, with said first parison being between said first inner mold section and said first outer mold section and said second parison being between said second inner mold section and said second outer mold section;   (e) simultaneously injecting gas into the interiors of said first parison between said first inner and outer mold sections, and into said second parison between said second inner and outer mold sections while said mold sections are in said closed position thereby blow molding said parisons.   
     
     
       4. The method of claim 3, including resiliently positioning said central platen, whereby said central platen adjusts in response to unequal pressure when said mold sections are moved to said closed positions.